The pressure at which typical gas distribution systems supply gas may vary according to the demands placed on the system, the climate, the source of supply, and/or other factors. However, most end-user facilities equipped with gas appliances such as furnaces, ovens, etc., require the gas to be delivered in accordance with a predetermined pressure, and at or below a maximum capacity of a gas regulator. Therefore, gas regulators are implemented into these distribution systems to ensure that the delivered gas meets the requirements of the end-user facilities. Conventional gas regulators generally include a closed-loop control actuator for sensing and controlling the pressure of the delivered gas.
In addition to a closed loop control, some conventional gas regulators include a relief valve. The relief valve is adapted to provide over pressure protection when the regulator or some other component of the fluid distribution system fails, for example. Accordingly, in the event the delivery pressure rises above a predetermined threshold pressure, the relief valve opens to exhaust at least a portion of the gas to the atmosphere, thereby reducing the pressure in the system.
FIGS. 1 and 2 depict one conventional gas regulator 10. The regulator 10 generally comprises an actuator 12 and a regulator valve 14. The regulator valve 14 defines an inlet 16 for receiving gas from a gas distribution system, for example, and an outlet 18 for delivering gas to an end-user facility such as a factory, a restaurant, an apartment building, etc. having one or more appliances, for example. Additionally, the regulator valve 14 includes a valve port 20 disposed between the inlet and the outlet. Gas must pass through the valve port 20 to travel between the inlet 16 and the outlet 18 of the regulator valve 14.
The actuator 12 is coupled to the regulator valve 14 to ensure that the pressure at the outlet 18 of the regulator valve 14, i.e., the outlet pressure, is in accordance with a desired outlet or control pressure. The actuator 12 is therefore in fluid communication with the regulator valve 14 via a valve mouth 22 and an actuator mouth 24. The actuator 12 includes a control assembly 26 for sensing and regulating the outlet pressure of the regulator valve 14. Specifically, the control assembly 26 includes a diaphragm 28, a piston 30, and a control arm 32 having a valve disc 34. The conventional valve disc 34 includes a generally cylindrical body 36 and a sealing insert 38 fixed to the body 36. The valve body 36 may also include a circumferential flange 40 integrally formed therewith, as depicted in FIG. 2. The diaphragm 28 senses the outlet pressure of the regulator valve 14. The control assembly 26 further includes a control spring 42 in engagement with a top-side of the diaphragm 28 to offset the sensed outlet pressure. Accordingly, the desired outlet pressure, which may also be referred to as the control pressure, is set by the selection of the control spring 42.
The diaphragm 28 is operably coupled to the control arm 32, and therefore, the valve disc 34 via the piston 30, controls the opening of the regulator valve 14 based on the sensed outlet pressure. For example, when an end user operates an appliance, such as a furnace, for example, that places a demand on the gas distribution system downstream of the regulator 10, the outlet flow increases, thereby decreasing the outlet pressure. Accordingly, the diaphragm 28 senses this decreased outlet pressure. This allows the control spring 42 to expand and move the piston 30 and the right-side of the control arm 32 downward, relative to the orientation of FIG. 1 as shown in FIG. 2. This displacement of the control arm 32 moves the valve disc 34 away from the valve port 20 to open the regulator valve 14. FIG. 2 depicts the valve disc 34 in a normal, open operating position. So configured, the appliance may draw gas through the valve port 20 toward the outlet 18 of the regulator valve 14.
In the conventional regulator 10 depicted in FIG. 1, the control assembly 26 further functions as a relief valve, as mentioned above. Specifically, the control assembly 26 also includes a relief spring 44 and a release valve 46. The diaphragm 28 includes an opening 48 through a central portion thereof and the piston 30 includes a sealing cup 50. The relief spring 44 is disposed between the piston 30 and the diaphragm 28 to bias the diaphragm 28 against the sealing cup 50 to close the opening 48, during normal operation. Upon the occurrence of a failure such as a break in the control arm 32, the control assembly 26 is no longer in direct control of the valve disc 34 and inlet flow will move the valve disc 34 will move into an extreme open position. This allows a maximum amount of gas to flow into the actuator 12. Thus, as the gas fills the actuator 12, pressure builds against the diaphragm 28 forcing the diaphragm 28 away from the sealing cup 50, thereby exposing the opening 48. The gas therefore flows through the opening 48 in the diaphragm 28 and toward the release valve 46. The release valve 46 includes a valve plug 52 and a release spring 54 biasing the valve plug 52 into a closed position, as depicted in FIG. 2. Upon the pressure within the actuator 12 and adjacent the release valve 46 reaching a predetermined threshold pressure, the valve plug 52 displaces upward against the bias of the release spring 54 and opens, thereby exhausting gas into the atmosphere and reducing the pressure in the regulator 10.
A regulator's performance is dictated by the volume of a fluid that can be transferred downstream while maintaining a designated outlet pressure. In the conventional regulator 10, the control spring 42 inherently generates less force as it expands towards an uncompressed length when displacing the control arm 32 to open the valve port 20. Additionally, as the control spring 42 expands, the diaphragm 28 deforms, which increases the area of the diaphragm 28. The decreased force supplied by the control spring 42 and the increased area of the diaphragm 28 in this operational scenario combine to create a regulator response wherein the force provided by the control spring 42 cannot adequately balance the force generated by the diaphragm 28 thereby resulting in an outlet control pressure that is less than that originally set by the user. This phenomenon is known as “droop.” When “droop” occurs, the outlet pressure decreases below its set control pressure and the regulator 10 may not function as intended. As the outlet pressure decreases, the amount of fluid transferred while maintaining the outlet pressure range, also know as the rated flow value, is decreased. Consequently, a need exists for improving the performance of conventional regulators by reducing or eliminating the effects of “droop” on the regulator's ability to maintain the outlet control pressure at a desired setpoint pressure and to maximize the volume of fluid flowing through the regulator valve.
Another factor affecting the performance of the regulator 10 is the force of the upstream pressure on the valve disc 34. When the actuator 12 is in the open position as shown in FIG. 2, the upstream pressure of the fluid passing through the valve port 20 applies a force on the valve disc 34 in the direction of the open position. Consequently, the magnitude of the upstream pressure and its fluctuations can affect the performance of the actuator 12 in maintaining the downstream pressure at the desired setpoint pressure. For example, as the upstream pressure increases, a greater downstream pressure is necessary to cause the actuator assembly 26 to move the valve disc 34 toward the valve port 20 to decrease the fluid flow through the valve 14. The problem is heightened in regulators with larger port sizes that can experience higher inlet pressures. In some implementations, it is necessary to install regulators having lower rated capacities to avoid over pressurizing the downstream portion of the system. Consequently, a need further exists for gas regulators that are less sensitive to upstream pressure variations at the valve port.